The most common ways mice get in
- Gaps around pipes and cables where they enter the building, especially under sinks and behind appliances
- Air bricks and vents that are damaged or have no mesh
- Gaps under and around doors, particularly garage, shed and back doors
- Cracks in brickwork and foundations
- Damaged drains and underground pipes
- Gaps in the loft and eaves, where mice climb walls, pipes and trellis to reach the roof
- Through deliveries and stored items, such as boxes, bags and second-hand furniture
How to find the entry points
- Walk around the outside of the property and look for gaps, cracks and worn seals, especially at ground level and where services enter
- Look inside for droppings and greasy rub marks, which are often concentrated near the entry point
- Check lofts, garages, utility rooms and the back of kitchen cupboards
- Look for signs of gnawing around openings
How to block them
Mice can chew through foam, plastic, rubber and soft materials, so use something tougher:
- Metal mesh or wire wool pushed tightly into gaps and sealed with cement or filler
- Metal kick plates or draught strips on the bottom of doors
- Fine metal mesh over air bricks and vents
- Cement or mortar for cracks in brickwork
Reduce the reasons for them to come
Even with good proofing, mice will test your home if it offers food and shelter. Store food in sealed containers, deal with waste promptly, keep gardens tidy and avoid stacking wood or clutter against the walls.
When proofing is not enough
If mice are already inside, blocking holes can trap them in. Deal with the mice first, using the steps in our guide to how to get rid of mice, then proof the building. A professional can find hidden entry points and do the proofing for you. See how much pest control costs in the UK if you are weighing up the price.
Frequently asked questions
How small a hole can a mouse get through?
Around 6mm, about the width of a pencil. Check the figure against your preferred source, as estimates vary slightly.
Can mice get in through drains?
Yes. Damaged or poorly sealed drains and underground pipes can let mice in, and professional inspection can help.
Do mice come in from outside or are they already in the house?
Often both. Mice move in from outside, especially in autumn and winter, but once they are in they breed quickly.
Need help finding the gaps?
Visit anticimex.co.uk to ask our team for a property inspection and proofing advice.